Comparison of the integral dose (ID) delivered to organs at risk (OAR), non-target body and target body by using different techniques of craniospinal irradiation (CSI).

Ten CSI patients (medulloblastoma) already planned and treated either with linear accelerator three-dimensional conformal radiation therapy (Linac-3DCRT) technique or with linear accelerator RapidArc (Linac-RapidArc) technique by Novalis-Tx Linac machine have been analysed. Retrospectively, these patients are again planned on Radixact-X9 Linac with Helical, Direct-3DCRT and Direct-intensity-modulated radiation therapy (Direct-IMRT) techniques. The dose prescription to planning target volume brain (PTV-Brain) and PTV-Spine is 36 Gy in 20 fractions and is kept the same for all techniques. The target body, non-target body, OARs and total body dose are compared.

ID is lowest in the RapidArc plan for every patient in comparison to Helical and Direct-IMRT. The ID for Body-PTV was found slightly higher in the RapidArc plan in comparison to 3DCRT plans. But there is better normal tissue sparing for most of the OARs in RapidArc plans if it compares with 3DCRT plans.

RapidArc is a better alternative for the treatment of CSI. It provides better target coverage and better OARs sparing from any other treatment techniques.

To compare the dosimetric performance of flattening filter-free (FFF) beam and flattened beams (FBs) utilising volumetric-modulated arc therapy (VMAT) for craniospinal irradiation (CSI) planning.

Five medulloblastoma patients were randomly selected retrospectively and 40 plans were generated. The dose prescription to the planning target volume (PTV) was 36 Gy in 20 fractions. VMAT plans were created using 6 MV and 10 MV FB and FFF beam. Final dose calculations were performed using Acuros XB (AXB) and analytical anisotropic algorithm (AAA). Dosimetric parameters such as D98%, D95%, D50%, V110%, conformity index (CI), homogeneity index (HI), low-grade dose index, high-grade dose index, dose to the organ at risks (OARs) and normal tissue mean dose were noted. The effect of low-dose volume on normal tissue was also analysed.

The 6 MV and 10 MV flattened and FFF beam plan generates similar target coverage, and a significant difference was observed in the HI and CI. FFF beam plan produces lower doses in some of the OARs as compared to FB. Significant differences were also noted in monitor unit (MU), body-PTV mean dose and low-dose spillage regions (1–10 Gy) outside the PTV. In our study, 6 MV and 10 MV FFF beam beams need 23–25% more MUs to achieve planning goals when compared to FBs. The increased MUs in FFF plan decreases the body-PTV mean dose (0·07–0·09 Gy in 6 MV FFF and 0·31 Gy in 10 MV FFF in both algorithms) when compared to FB plans.

FFF beams generate a highly conformal and homogenous plan in CSI cases. FFF beam plan reduced the non-tumour dose and will aid in reducing the probability of second malignancies.

The purpose of this study was to dosimetrically compare TomoDirect, TomoHelical and linear accelerator-based 3D-conformal radiotherapy (Linac-3DCRT) for craniospinal irradiation (CSI) in the treatment of medulloblastoma.

Five CSI patients were replanned with Linac-3DCRT, TomoHelical, TomoDirect-3DCRT and TomoDirect-intensity-modulated radiotherapy (IMRT). Dose of 36 Gy in 20 fractions was prescribed to the planning target volume (PTV). Homogeneity index (HI), non-target integral dose (NTID), dose–volume histograms, organs-at-risk (OARs) Dmax, Dmean and treatment times were compared.

TomoHelical achieved the best PTV homogeneity compared with Linac-3DCRT, TomoDirect-3DCRT and TomoDirect-IMRT (HI of 3·6 versus 20·9, 8·7 and 9·4%, respectively). TomoDirect-IMRT achieved the lowest NTID compared with TomoDirect-3DCRT, TomoHelical and Linac-3DCRT (141 J versus 151 J, 181 J and 250 J), indicating least biological damage to normal tissues. TomoHelical plans achieved the lowest Dmax in all organs except the breasts, and lowest Dmean for most OARs, except in laterally situated OARs, where TomoDirect triumphed. Beam-on time was longest for TomoHelical, followed by TomoDirect and Linac-3DCRT.

TomoDirect has the potential to lower NTID and shorten treatment times compared with TomoHelical. It reduces PTV inhomogeneity and better spares OARs compared with Linac-3DCRT. Therefore, TomoDirect may be a CSI treatment alternative to TomoHelical and in place of Linac-3DCRT.

Craniospinal irradiation (CSI) has become an important and challenging radiation technique for radiation oncologists. Helical tomotherapy (HT) seems to have dosimetric advantage for CSI compared with other radiation modalities. The purpose of this study was to compare dosimetric data between two different HT plans; simultaneous integrated boost (SIB) and sequential boost (Sq).

Twelve previously treated CSI contoured datasets by SIB technique were replanned. Dosimetric comparative parameters of targets were conformity index (CI) and homogeneity index (HI). For organ at risk (OARs), the mean dose of parallel organs, D2% of serial organs and whole body integral dose (ID) were also investigated.

SIB plan significantly provided more conformed dose to CSI and tumour boost while resulting in a similar CI in spinal boost region compared with Sq plan. The HI showed no differences between two plans. Radiation exposure to serial organs and ID were also significantly lower in SIB plan.

CSI treatment using HT, SIB technique was feasible and had more target coverage while minimising the radiation dose to healthy tissues.